If I may rephrase; a vacuum could be created with the passage of the faster moving airstream, relative to the slower air mass exiting from the cowling which could be at a lower pressure then the passing airstream.
When I did my differential air pressure tests I did not test the relative pressure exiting the cowling relative to the airstream around the bottom of the fuselage. I will refrain, in the future, from using speculation.
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average
speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger flying #153
St.Thomas, Ontario Canada, CYQS
Last edited by Tom Martin : 04-18-2018 at 09:55 AM.